1. Field of the Invention
This invention relates to a tire chain mounting device and a method therefor used with an automotive vehicle traveling on a snow road.
2. Description of the Prior Art
It is very difficult and troublesome to mount a tire chain onto a tire of the automotive vehicle. In particular, winding the tire chain round an outer periphery of the tire is most troublesome. Hithertofore, various types of tire chain mounting device have been developed which have a pair of fixedly spaced arms for transversely and elastically clamping the opposite side portions of the tire tread and have a lug on each arm for engaging a second ring from an end of the tire chain. These types of tire chain mounting device can readily and promptly wind the tire chain round the outer periphery of the tire by means of turning the tire once along a road.
However, a breadth of the tire of the automotive vehicle includes more than about 35 classes in accordance with JIS, e.g. ranging from a class of about 130 mm to a class above 209 mm and one tire chain mounting device of the above-described types can be used with only one class of tire breadth because the above-described types of tire chain mounting device have the fixedly spaced arms. Therefore, when a person has more than one automotive vehicles one having a set of tires with a tire breadth different from a tire breadth of a set of tires of other automotive vehicles, or when a tire breadth is changed by a replacement of a set of tires for the same automotive vehicle, he must provide different tire chain mounting devices for at least two classes of tire breadth.
In order to overcome the above-described disadvantage, some types of tire chain mounting device have been developed which can adjust a spacing between a pair of opposite arms in accordance with various classes of tire breadth. For example, JP-Y-56-46936 or JP-U-60-47607 discloses such type of tire chain mounting device.
JP-Y-56-46936 discloses a tire chain mounting device comprising a pair of opposite arms for clamping the opposite side walls of a tire; two lugs for engaging a part of a tire chain, each lug integrally formed with each arm; a pair of rigid bars extending perpendicularly to an axis of one arm from an end of the arm to an end of the other arm; a member for fixing the bars overlapping each other in a range of a preadjusted length; and a plurality of gauge marks for indicating specific spacings between the opposite arms produced by means of overlapping the bars.
According to this tire chain mounting device, the bars must be rigid because they continuously mesh each other by means of their rack teeth. The rigidity of the overlapped bars blocks flexibility in the spacing between the opposite arms once the spacing has been fixed. When a person mounts the tire chain mounting device onto the tire, he must usually check a gauge mark of the tire breadth provided on the side wall of the tire and select a corresponding gauge mark on the tire chain mounting device in order to adjust the spacing between the arms. In other words, he cannot adjust the spacing between the arms in accordance with a tire tread breadth (somewhat narrower than the tire breadth between the tire side walls) by means of bringing the arms into contact directly with the opposite edges of the tire tread. Consequently, a clamping force of the arms produced by only an elastic force of the arm is small and thereby the tire chain mounting device is inclined to detach from the tire.